When reading the doc, be careful about the term 'record'. For a physical device, 'record' means 'block' because the device has no notion of logical structure. As already pointed out, BSAM read returns an entire block (as in BLKSIZE) and leaves the task of segmenting into logical records entirely up to you. Some doc might use 'record' for what we understand as 'block'.
By contrast, QSAM fetches a block (as necessary) and returns to your program one logical record at a time. The downside of QSAM is that your program enters an implicit WAIT on each read or write. Why a modern application would want to undertake the complexity of BSAM--unless required as discussed earlier--would be hard to argue. BTW as a nascent application programmer, I was advised to use GET LOCATE and PUT MOVE for simplest coding. . . J.O.Skip Robinson Southern California Edison Company Electric Dragon Team Paddler SHARE MVS Program Co-Manager 323-715-0595 Mobile 626-543-6132 Office ⇐=== NEW robin...@sce.com -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Blaicher, Christopher Y. Sent: Friday, February 03, 2017 11:50 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: (External):Re: BSAM vs QSAM Careful on reusing that buffer before the ECB is posted in the write. You could wind up overlaying what is in the middle of being written. It is not safe to reuse the buffer before the ECB is posted. You may get away with it most of the time, but if there is an error and the channel re-drives the I/O you may have laid new data in the buffer before the write is done. Chris Blaicher Technical Architect Mainframe Development Syncsort Incorporated 2 Blue Hill Plaza #1563, Pearl River, NY 10965 P: 201-930-8234 | M: 512-627-3803 E: cblaic...@syncsort.com www.syncsort.com CONNECTING BIG IRON TO BIG DATA -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Farley, Peter x23353 Sent: Friday, February 3, 2017 2:42 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: BSAM vs QSAM BSAM only gets you an entire block on a READ. You have to extract each varying record from the block with your own code. On a WRITE you have to give it an entire block, BDW + one or more RDW + record. You have to construct the block yourself in your own code before you issue the WRITE. OTOH you don't have to wait for completion of a READ or a WRITE. You can issue a WRITE at the end of a processing loop and then go back to process the next record while the WRITE completes, and only CHECK the WRITE when you are ready to issue the next WRITE. Similarly for READ's, issue another READ right after the start of processing for the prior record, then CHECK the second READ when you come back to the top of the processing loop. Complicated, but it can provide improved (FSVO improved) elapsed time by overlapping processing with I/O rather than processing synchronously. HTH Peter -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Joseph Reichman Sent: Friday, February 03, 2017 2:27 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: BSAM vs QSAM I have huge VB files Don't really understand what you mean by Deblock after doing a READ then WAIT Where an entire block is read subsequent READs Just point to the next record > On Feb 3, 2017, at 2:22 PM, Blaicher, Christopher Y. <cblaic...@syncsort.com> > wrote: > > There can be if you code for just what you expect. > > QSAM does multi-buffer I/O for you, with BSAM you have to issue multiple > WRITE or REAAD commands and do a WAIT, not to mention having to block or > de-block the buffer, which can be a real pain for VBS files. > > It really depends on how much you are processing and how often you are doing > it to determine if the amount of time you are going to spend on developing it > makes it worth it. > > Using QSAM with GET LOCATE (as long as you aren't processing VBS files) and a > reasonable BUFNO of 10 or more is going to get you close to most BSAM > applications. GET or PUT with the MOVE option is the easiest to code for. > > Chris Blaicher > Technical Architect > Mainframe Development > Syncsort Incorporated > 2 Blue Hill Plaza #1563, Pearl River, NY 10965 > > P: 201-930-8234 | M: 512-627-3803 > E: cblaic...@syncsort.com > > www.syncsort.com > > CONNECTING BIG IRON TO BIG DATA > > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] > On Behalf Of Joseph Reichman > Sent: Friday, February 3, 2017 1:51 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: BSAM vs QSAM > > Hi > > BSAM is a bit more complex than QSAM > > Is there any performance improvement > > Thanks ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
